406 satellite beacon phase modulation method and apparatus

Abstract

The application discloses a 406 satellite position indication phase modulation method and device, comprising the following steps: S1: selecting at least three stable frequencies as a group according to the FSK modulation mode, generating corresponding intermediate frequencies H, and then adjusting the carrier nominal frequency according to the intermediate frequencies, so that the intermediate adjustment frequency is 406.031MHz, and adjustment information is obtained, including the adjustment frequency corresponding to the original stable frequency, adjustment data, relative frequency offset and phase migration time; S2: processing the 406 satellite position indication message framing signal, and converting it into modulation data according to the adjustment information; S3: correcting the carrier frequency according to the adjustment information, and obtaining the modulation frequency; S4: sending the modulation data by using the modulation frequency, and the modulation frequency corresponds to the modulation data at the same time. The application realizes the phase modulation by using the frequency offset modulation, and the phase modulation can be realized by using the low-cost radio frequency transceiver chip without the phase modulation function.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of communication, and particularly relates to a 406 satellite beacon phase modulation method and device. BACKGROUND

[0002] The 406 satellite beacon has important value in the fields of navigation and aviation, and provides the most extensive and basic communication guarantee for navigation safety and aviation safety.

[0003] In the 406 satellite beacon, a digital communication technology based on phase modulation is adopted, the baseband rate of the 406 satellite beacon is 400 bps, in order to introduce clock information in the signal, the line coding adopts biphase L, that is, symbol 1 is mapped into (+1, 0), and symbol 0 is mapped into (0, +1), so as to avoid the loss of the clock signal due to long '1' or long '0'.

[0004] In the physical layer, +1 corresponds to a phase of +1.1 rad (radians, leading the carrier phase), and 0 corresponds to -1.1 rad (radians, lagging the carrier phase), as shown in the following formula: Figure 1

[0005] Further, in the specification, in order to transmit the carrier frequency information and the phase information, whether for a long frame or a short frame, a fixed-length carrier-free signal, that is, a non-modulated carrier, needs to be sent before the message is sent, and the length of the carrier-free signal is 160 ms. The time for phase climbing and rolling down and the symmetry requirement are as follows (t r represents the phase climbing time, and t f represents the phase rolling down time):

[0006] 50 μs≤t r ≤250 μs;

[0007] 50 μs≤t f ≤250 μs;

[0008]

[0009] However, the existing radio frequency transceiver chip with phase modulation function has high cost and high price, and is not suitable for wide promotion. SUMMARY

[0010] In order to solve the above technical problems, the application provides a 406 satellite beacon phase modulation method and device.

[0011] In order to achieve the above purpose, the technical scheme of the application is as follows:

[0012] On the one hand, the application discloses a 406 satellite beacon phase modulation method, comprising:

[0013] ​Step S1: According to the FSK modulation mode, there are k1 different steady-state frequencies, and k2 steady-state frequencies are selected as a group to generate corresponding intermediate frequencies H, and then the carrier nominal frequency is adjusted according to the intermediate frequency, so that the intermediate adjustment frequency is the expected frequency, wherein: k2 < k1, and k2 ≥ 3;

[0014] The adjustment information includes: the adjustment frequency corresponding to the original steady-state frequency, the adjustment data, the relative frequency offset, and the phase migration time;

[0015] Step S2: Process the 406 satellite indication message framing signal, and convert it into modulation data according to the adjustment information;

[0016] Step S3: According to the adjustment information, the carrier frequency is frequency corrected to obtain the modulation frequency;

[0017] Step S4: Use the modulation frequency to send the modulation data, and the modulation frequency corresponds to the modulation data at the same time.

[0018] On the basis of the above technical solutions, the following improvements can be made:

[0019] As a preferred solution, step S2 specifically includes:

[0020] Step S2.1: Obtain the 406 satellite indication message framing signal of the binary code stream;

[0021] Step S2.2: Perform Biphase L encoding on the 406 satellite indication message framing signal of the binary code stream to form n bit encoding data;

[0022] Step S2.3: Initialize the n bit encoding data;

[0023] Step S2.4: Expand the n bit encoding data into a data group, and 1 bit encoding data corresponds to xB data;

[0024] Step S2.5: Modulate each bit encoding data according to the adjustment information to obtain the modulation data.

[0025] As a preferred solution, step S2.5 specifically includes:

[0026] Step S2.5.1: Judge the 1st bit encoding data,

[0027] If it is 1, the 1st xB data is corrected according to the adjustment information, so that its phase is adjusted from 0 rad to +1.1 rad;

[0028] If it is 0, the 1st xB data is corrected according to the adjustment information, so that its phase is adjusted from 0 rad to -1.1 rad;

[0029] Step S2.5.2: judging the i-th bit encoding data, i=2,…n;

[0030] If the (i-1)-th bit encoding data is same as the i-th bit encoding data, the corresponding xB data is maintained unchanged;

[0031] If the (i-1)-th bit encoding data is 0 and the i-th bit encoding data is 1, the corresponding xB data is modified according to the adjustment information, so that the phase is adjusted from -1.1 rad to +1.1 rad;

[0032] If the (i-1)-th bit encoding data is 1 and the i-th bit encoding data is 0, the corresponding xB data is modified according to the adjustment information, so that the phase is adjusted from +1.1 rad to -1.1 rad;

[0033] Step S2.5.2 is repeated until all encoding data is modulated to obtain the corresponding modulation data.

[0034] As a preferred scheme, the intermediate frequency H is obtained by the following formula:

[0035]

[0036] wherein: h j is the j-th steady-state frequency.

[0037] As a preferred scheme, the 406 satellite beacon message framing signal comprises a long frame signal or a short frame signal.

[0038] As a preferred scheme, the 406 satellite beacon phase modulation method is based on 4FSK modulation mode.

[0039] As a preferred scheme, in step S1, the steady-state frequencies with number 0, number 1, and number 2 are selected as a group, or the steady-state frequencies with number 1, number 2, and number 3 are selected as a group.

[0040] wherein: the steady-state frequency with number 0 is fc-Δf, the steady-state frequency with number 1 is fc-Δf / 3, the steady-state frequency with number 2 is fc+Δf / 3, and the steady-state frequency with number 3 is fc+Δf.

[0041] When the steady-state frequencies with number 0, number 1, and number 2 are selected as a group, the intermediate frequency H is fc-Δf / 3, and then the carrier nominal frequency is adjusted upward by Δf / 3 according to the intermediate frequency, to obtain the adjustment frequency with number 0 as fc-2*Δf / 3, the adjustment frequency with number 1 as 0, the adjustment frequency with number 2 as fc+2*Δf / 3, and the adjustment frequency with number 3 as fc+4*Δf / 3.

[0042] When the steady-state frequencies of the numbers 1, 2 and 3 are selected as a group, the intermediate frequency H is fc+Δf / 3, and then the carrier nominal frequency is adjusted downward by Δf / 3 according to the intermediate frequency, so that the adjustment frequency of the number 0 is fc-4*Δf / 3, the adjustment frequency of the number 1 is fc-2*Δf / 3, the adjustment frequency of the number 2 is 0, and the adjustment frequency of the number 3 is fc+2*Δf / 3.

[0043] In another aspect, the application also discloses a 406 satellite beacon phase modulation device, comprising:

[0044] A reference crystal oscillator is used to provide a reference frequency for the MUC;

[0045] An MCU is used to control the radio frequency transceiver chip.

[0046] A radio frequency transceiver chip is electrically connected with the MUC and is used to execute any of the 406 satellite beacon phase modulation methods.

[0047] As a preferred scheme, the PLL circuit inside the MCU can synthesize clock information for the radio frequency transceiver chip.

[0048] As a preferred scheme, the 406 satellite beacon phase modulation device further comprises a power amplifier chip electrically connected with the radio frequency transceiver chip and used to realize signal amplification.

[0049] The application discloses a 406 satellite beacon phase modulation method and device, which realizes phase modulation by frequency offset modulation, and can realize phase modulation by using a low-cost radio frequency transceiver chip without phase modulation function, and is suitable for wide range of promotion and application. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be considered as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0051] Figure 1 A 406 satellite beacon double-phase encoding waveform diagram provided by the prior art.

[0052] Figure 2 A flowchart of the 406 satellite beacon phase modulation method provided by the embodiments of the application.

[0053] Figure 3 A block diagram of the 406 satellite beacon phase modulation device provided by the embodiments of the application.

[0054] Figure 4A schematic diagram of an MCU internal PLL circuit provided by an embodiment of the present application.

[0055] Figure 5 A 4FSK modulation symbol and frequency correspondence diagram provided by an embodiment of the present application. DETAILED DESCRIPTION

[0056] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0057] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application.

[0058] The expression of "comprising" elements is an "open" expression, which only means that the corresponding components or steps exist, and should not be interpreted as excluding additional components or steps.

[0059] In order to achieve the purpose of the present application, as shown in FIG. 6, the 406 satellite beacon phase modulation method includes the following steps. Figure 2

[0060] Step S1: According to the 4FSK modulation mode, there are four different steady-state frequencies, three of which are selected as a group to generate the corresponding intermediate frequency H, and then the carrier nominal frequency is adjusted according to the intermediate frequency, so that the intermediate adjustment frequency is 406.031MHz (or other frequency points, adjusted according to the specification);

[0061] The adjustment information includes: the adjustment frequency corresponding to the original steady-state frequency, the adjustment data, the relative frequency offset and the phase migration time;

[0062] Step S2: Process the 406 satellite beacon message framing signal, and convert it into modulation data according to the adjustment information, wherein: the 406 satellite beacon message framing signal includes a long frame signal or a short frame signal, the length of the long frame signal is 144bit, and the length of the short frame signal is 112bit;

[0063] Step S3: According to the adjustment information, the carrier frequency is frequency corrected to obtain the modulation frequency;

[0064] Step S4: The modulation frequency is used to send the modulation data, and the modulation frequency corresponds to the modulation data at the same time.

[0065] ​Further, the steady-state frequencies of the No. 0, No. 1 and No. 2 are selected as a group, or the steady-state frequencies of the No. 1, No. 2 and No. 3 are selected as a group.

[0066] Wherein: the steady-state frequency of the No. 0 is fc-Δf, the steady-state frequency of the No. 1 is fc-Δf / 3, the steady-state frequency of the No. 2 is fc+Δf / 3, and the steady-state frequency of the No. 3 is fc+Δf.

[0067] When the steady-state frequencies of the No. 0, No. 1 and No. 2 are selected as a group, the intermediate frequency H is fc-Δf / 3, and then the carrier nominal frequency is adjusted upward by Δf / 3 according to the intermediate frequency, so as to obtain the adjusted frequency of the No. 0 as fc-2*Δf / 3, the adjusted frequency of the No. 1 as 0, the adjusted frequency of the No. 2 as fc+2*Δf / 3, and the adjusted frequency of the No. 3 as fc+4*Δf / 3.

[0068] When the steady-state frequencies of the No. 1, No. 2 and No. 3 are selected as a group, the intermediate frequency H is fc+Δf / 3, and then the carrier nominal frequency is adjusted downward by Δf / 3 according to the intermediate frequency, so as to obtain the adjusted frequency of the No. 0 as fc-4*Δf / 3, the adjusted frequency of the No. 1 as fc-2*Δf / 3, the adjusted frequency of the No. 2 as 0, and the adjusted frequency of the No. 3 as fc+2*Δf / 3.

[0069] Further, the step S2 specifically comprises:

[0070] Step S2.1: obtaining the 406 satellite indication bit message framing signal of the binary code stream;

[0071] Step S2.2: performing bi-phase L encoding on the 406 satellite indication bit message framing signal of the binary code stream, to form n bit encoding data, wherein: the encoding data length of the long frame signal is 288 bits, and the encoding data length of the short frame signal is 224 bits;

[0072] Step S2.3: initializing the n bit encoding data;

[0073] Step S2.4: expanding the n bit encoding data into data groups, and 1 bit encoding data corresponds to 3B data;

[0074] Step S2.5: modulating each bit encoding data according to the adjustment information, to obtain modulated data.

[0075] Further, the step S2.5 specifically comprises:

[0076] Step S2.5.1: judging the first bit encoding data,

[0077] If 1, the first 3B data is corrected according to the adjustment information, so that the phase is adjusted from 0 rad to +1.1 rad;

[0078] If 0, the first 3B data is corrected according to the adjustment information, so that the phase is adjusted from 0 rad to -1.1 rad;

[0079] Step S2.5.2: judging the i-th bit encoding data, i=2,…n;

[0080] If the (i-1)-th bit encoding data is the same as the i-th bit encoding data, the corresponding 3B data is maintained unchanged;

[0081] If the (i-1)-th bit encoding data is 0 and the i-th bit encoding data is 1, the corresponding 3B data is corrected according to the adjustment information, so that the phase is adjusted from -1.1 rad to +1.1 rad;

[0082] If the (i-1)-th bit encoding data is 1 and the i-th bit encoding data is 0, the corresponding 3B data is corrected according to the adjustment information, so that the phase is adjusted from +1.1 rad to -1.1 rad;

[0083] Step S2.5.2 is repeated until all encoding data is modulated to obtain the corresponding modulation data.

[0084] In addition, the embodiment of the present application also discloses a 406 satellite beacon phase modulation device, as shown in the figure, comprising: Figure 3

[0085] Reference crystal oscillator, used to provide reference frequency for MUC;

[0086] MCU, used to realize the control of the radio frequency transceiver chip;

[0087] Radio frequency transceiver chip, electrically connected with MUC, used to execute the 406 satellite beacon phase modulation method disclosed in any of the above embodiments.

[0088] The PLL circuit inside the MCU can synthesize clock information for the radio frequency transceiver chip.

[0089] Further, the 406 satellite beacon phase modulation device further comprises: a power amplifier chip, electrically connected with the radio frequency transceiver chip, used to realize signal amplification.

[0090] ​For the convenience of understanding the present application, the following specific embodiments are given, the radio frequency transceiver chip adopts CMT2310A, CMT2310A is a general-purpose SOC chip supporting OOK, FSK / GFSK, 4FSK / 4GFSK modulation and demodulation, the host chip sets the working mode (such as modulation and demodulation mode, baseband rate, frequency offset size) of CMT2310A through SPI (serial peripheral interface), and also writes the modulation data into the CMT2310A sending buffer through SPI for internal modulation.

[0091] Although the present embodiment takes CMT2310A chip as the radio frequency transceiver chip, the method is applicable to any other chip similar to CMT2310A, such as SI4463, etc.

[0092] As shown in Figure 4 , the reference crystal in the figure provides a reference frequency for the MCU, and the frequency selection is relatively flexible, such as 14.4MHz, 16.8MHz or 19.2MHz, etc. In the MCU, after frequency division and frequency multiplication, a suitable bus clock (such as 32MHz or other frequencies, etc.) is obtained.

[0093] The MCU and CMT2310A are connected through four groups of lines, namely SPI bus, interrupt, GPIO and 32MHz clock.

[0094] Among them: the SPI bus is used for bidirectional communication between the MCU and CMT2310A, such as configuring the working mode of CMT2310A, reading the working state of CMT2310A, etc. The interrupt bus is used for CMT2310A to inform the MCU of CMT2310A events, so that the MCU can respond in time and make corresponding processing. The GPIO is used to control the working state of CMT2310A and as input in low-speed binary modulation (such as OOK modulation, 2FSK modulation and 2GFSK modulation, etc.). The 32MHz clock is generated from the MCU internally, in the MCU, the external reference crystal is frequency divided and multiplied by a set of internal PLL to obtain a 32MHz reference clock for CMT2310A.

[0095] As shown in Figure 3 , the 32MHz clock information is synthesized by the internal PLL circuit of the MCU for CMT2310A.

[0096] The reference crystal oscillation frequency is theoretically not limited, as long as the following requirements are met, and Where fr is the reference crystal, and N, M are integers.

[0097] By synthesizing 32MHz clock internally, the mandatory requirement of reference clock for CMT2310A can be effectively eliminated, and any marine certified crystal product can be selected, without the need of customizing 32MHz crystal and performing marine certification, effectively reducing product price and cost, and providing a wider selection range for selecting crystal.

[0098] To meet the specification requirement of 406 satellite beacon, CMT2310A needs to be set to appropriate mode first, as follows:

[0099] Table 1, CMT2310A working mode setting

[0100]

[0101]

[0102] According to the above requirements, CMT2310A is set to the specified working mode through SPI interface.

[0103] The above parameters can actually be generated by the automatic configuration tool of CMT2310A, i.e. RFPDK, to obtain a configuration file header file cmt2310a_params.h, which configures the internal registers according to the above requirements. The parameters of the configuration file can be written into the corresponding configuration registers through SPI interface.

[0104] Phase modulation is realized by 4FSK, and the principle is as follows: when the phase needs to be advanced or lagged, the frequency is up or down and runs for a period of time.

[0105] According to the above configuration parameters, a 4FSK modulated signal with 406.031MHz as the center frequency is obtained, as shown in Figure 5

[0106] In 4FSK modulation mode, the carrier frequency can only be stably operated at the frequencies corresponding to numbers 0, 1, 2 and 3, and can only be temporarily across 406.031MHz (or other frequency points, adjusted according to the specification).

[0107] Specifically:

[0108] The steady-state frequency of number 0 (corresponding to symbol -3) is 406.031MHz-2.521kHz, the steady-state frequency of number 1 (corresponding to symbol -1) is 406.031MHz-0.840kHz, the steady-state frequency of number 2 (corresponding to symbol +1) is 406.031MHz+0.840kHz, and the steady-state frequency of number 3 (corresponding to symbol +3) is 406.031MHz+2.521kHz.

[0109] ​In order to make the carrier frequency stable at 406.031 MHz, three steady frequencies are selected as a group. (3, 2, 1) can be selected as a group, or (2, 1, 0) can be selected as a group. These two selections are equivalent.

[0110] When the symbol +3 (0b11) is input to the internal 4FSK modulator of the CMT2310A, the frequency is stable at 406.031 MHz + 2.521 kHz, when the symbol +1 (0b10) is input to the internal 4FSK modulator, the frequency is stable at 406.031 MHz + 0.840 kHz, and when the symbol -1 (0b01) is input to the 4FSK modulator, the frequency is stable at 406.031 MHz - 0.840 kHz. When (3, 2, 1) is selected as a group, it is obvious that the intermediate frequency H is 406.031 MHz + 0.840 kHz, and when (2, 1, 0) is selected as a group, the intermediate frequency H is 406.031 MHz - 0.840 kHz.

[0111] When the group is selected, the frequency is adjusted. When (3, 2, 1) is selected as a group, the nominal frequency of the 4FSK carrier is lowered by 0.840 kHz (2.521 kHz / 3), and the nominal frequency of the 4FSK carrier is 406.031 MHz - 0.840 kHz. In this case, the adjusted frequency corresponding to the symbol +1 is 406.031 MHz, the adjusted frequency corresponding to the symbol -1 is 406.031 MHz - 0.840 kHz, and the adjusted frequency corresponding to the symbol +3 is 406.031 MHz + 0.840 kHz.

[0112] When (2, 1, 0) is selected as a group, the nominal frequency of the 4FSK carrier is raised by 0.840 kHz, and the purpose is to ensure that the intermediate modulation frequency is always 406.031 MHz (or other frequency, adjusted according to the specification, the same below) in the selected group, to meet the 406 satellite beacon specification requirements.

[0113] Taking the (3, 2, 1) group as an example, the adjustment information is shown in Table 2.

[0114] Table 2, modulation frequency and phase migration time

[0115]

[0116] As shown in Table 2, phase modulation can be achieved by temporarily adjusting the modulation frequency. When no phase adjustment is required or the phase adjustment is in place, the modulation frequency is set at 406.031 MHz, i.e. the corresponding symbol is +1, and the corresponding binary data is 0b10.

[0117] Further, the 406 satellite beacon original data rate is 400bps, and the data link layer symbol rate is 800Sps after line coding. Since the 4FSK symbol rate is 9.6kSps, i.e. 9600Sps, one data is expanded into 12 symbols, of which the first two symbols are used for phase adjustment, and the remaining 10 symbols are used for phase maintenance. When the unmodulated carrier ends, the phase is 0, and only one symbol period is needed to adjust the phase to +1.1 rad or -1.1 rad, i.e. for the first phase adjustment, only one symbol is used, and the remaining 11 symbols are used for phase maintenance.

[0118] In 4FSK, one symbol occupies 2b, so 12 symbols require 24b, i.e. 3B is required.

[0119] For the 406 satellite beacon, taking a long frame signal as an example, a long frame signal has 144 bits in total, which becomes 288 bits after line coding, and each bit occupies 3B, so a long frame requires 288*3=864B space.

[0120] Since the 4FSK modulated signal runs at 406.031MHz for part of the time, the 864B bytes can be initialized to 0x55 (sent from high to low, i.e. MSB first, so 0b01010101=0x55). In order to realize phase modulation, the 864B bytes are divided into 288 groups, i.e. 3B for a group, and only the first 2 bits or 4 bits of each group need to be adjusted to realize phase modulation.

[0121] According to the above adjustment information,

[0122] For example, when the phase needs to be adjusted from 0 rad to +1.1 rad, only the first 0b01 needs to be adjusted to 0b10, i.e. 0b010101010101010101010101 is adjusted to 0b100101010101010101010101, i.e. 0x555555 is adjusted to 0x955555.

[0123] When the phase needs to be adjusted from 0 rad to -1.1 rad, only the first 0b01 needs to be adjusted to 0b00, i.e. 0b010101010101010101010101 is adjusted to 0b000101010101010101010101, i.e. 0x555555 is adjusted to 0x155555.

[0124] When the phase needs to be adjusted from -1.1 rad to +1.1 rad, only the initial 0b0101 needs to be adjusted to 0b1010, i.e., 0b010101010101010101010101 is adjusted to 0b101001010101010101010101, i.e., 0x555555 is adjusted to 0xA55555.

[0125] When the phase needs to be adjusted from +1.1 rad to -1.1 rad, only the initial 0b0101 needs to be adjusted to 0b0000, i.e., 0b010101010101010101010101 is adjusted to 0b000001010101010101010101, i.e., 0x555555 is adjusted to 0x055555.

[0126] The following is an example of a long frame signal, and the 406 satellite marker phase modulation method includes:

[0127] Step S1: According to the 4FSK modulation mode, there are four different steady-state frequencies, and three steady-state frequencies of codes 1, 2 and 3 are selected as a group to generate the corresponding intermediate frequency H, and then the carrier nominal frequency is adjusted according to the intermediate frequency;

[0128] The adjustment information is obtained, as shown in Table 2, including: the adjustment frequency of the corresponding original steady-state frequency, the adjustment data, the relative frequency offset and the phase migration time;

[0129] Step S2 is specifically:

[0130] Step S2.1: Obtain the 406 satellite marker message framing signal of the binary code stream, and the length of the long frame signal is 144 bits;

[0131] Step S2.2: Perform Biphase L encoding on the 406 satellite marker message framing signal of the binary code stream, and the encoding mode is as follows: 1 is mapped into (1, 0) pair, and 0 is mapped into (0, 1) pair, forming 288 bit encoding data;

[0132] Step S2.3: Initialize a 16-bit unsigned integer array with a length of 864B to 0x55 (or 0xAA, only 0x55 is taken as an example here);

[0133] Step S2.4: Expand the 288 bit encoding data into a data group, and 1 bit encoding data corresponds to 3B data, and the order is increased;

[0134] Step S2.5: Each bit encoding data is modulated according to the adjustment information to obtain the modulation data, and the specific modulation method includes:

[0135] Step S2.5.1: judging the first bit encoded data,

[0136] If 1, the first 3B data 0x555555 is modified to 0x955555, and its phase is adjusted from 0 rad to +1.1 rad;

[0137] If 0, the first 3B data 0x555555 is modified to 0x155555, and its phase is adjusted from 0 rad to -1.1 rad;

[0138] Step S2.5.2: judging the i-th bit encoded data, i = 2, …, 288;

[0139] If the (i-1)-th bit encoded data is same as the i-th bit encoded data, the corresponding 3B data is maintained unchanged;

[0140] If the (i-1)-th bit encoded data is 0, and the i-th bit encoded data is 1, the corresponding 3B data is modified from 0x555555 to 0xA55555, and its phase is adjusted from -1.1 rad to +1.1 rad;

[0141] If the (i-1)-th bit encoded data is 1, and the i-th bit encoded data is 0, the corresponding 3B data 0x555555 is modified to 0x055555, and its phase is adjusted from +1.1 rad to -1.1 rad;

[0142] Step S2.5.2 is repeated until all encoded data are modulated, and the corresponding modulated data are obtained.

[0143] Step S3: according to the adjustment information, the carrier frequency is frequency-modified to obtain the modulated frequency, and the modification method is reconfiguration of CMT2310A, and the specific method is as follows:

[0144] Step S3.1: according to the working mode defined in Table 1, the corresponding configuration header file cmt2310a_params.h is obtained by using CMT2310A configuration tool software;

[0145] Step S3.2: read the 17th and 18th items in g_cmt2310a_page1[] in cmt2310a_params.h respectively, modify them and combine them into a 16-bit unsigned integer (the 18th item occupies the high 8 bits and the 17th item occupies the low 8 bits, totally 16 bits), add (for the (2, 1, 0) group) or subtract (for the (3, 2, 1) group) a correction value (the correction value is 220, i.e. 840Hz / 3.81Hz / bit≈220, wherein 3.81Hz / bit represents the frequency adjustment accuracy corresponding to the CMT2310A in the 406MHz frequency band, i.e. increasing or decreasing 1 bit of data will cause the oscillation frequency to increase or decrease 3.82Hz, if the adjustment is 840Hz, 220 need to be added or subtracted) to the value, obtain a new 16-bit unsigned integer, then write the low 8 bits of the integer to the 17th item in g_cmt2310a_page1[] and write the high 8 bits to the 18th item in the table, and then write the modified cmt2310a_params.h configuration parameter to the CMT2310A configuration register;

[0146] Step S4: transmit the modulation data using the modulation frequency, and at the same time, the modulation frequency corresponds to the modulation data, specifically, the CMT2310A is enabled to transmit at the same time, and the modulation data is sequentially written into the FIFO through the SPI interface (interruptive writing is needed) during transmission.

[0147] In step S3, the original configuration parameter can also be written first, and then the corresponding register value of the CMT2310A is directly modified.

[0148] The application discloses a 406 satellite beacon phase modulation method and device, which modulates the phase by frequency offset modulation, and can realize phase modulation by using a low-cost radio frequency transceiver chip without phase modulation function, and is suitable for wide range of promotion and application.

[0149] The above examples are only for illustrating the technical concept and characteristics of the application, and the purpose is to enable those skilled in the art to understand the content of the application and implement it, and cannot limit the protection scope of the application, and equivalent changes or modifications made according to the spirit and essence of the application should be covered in the protection scope of the application.

Claims

1. 406 A phase modulation method for a satellite beacon, characterized in that, The method comprises the following steps: Step S1: According to the 4FSK modulation mode, there are four different steady-state frequencies, three of which are selected as a group to generate the corresponding intermediate frequency H, and then the carrier nominal frequency is adjusted according to the intermediate frequency, so that the intermediate adjustment frequency is the expected frequency, thereby obtaining the adjustment information, including: the adjustment frequency corresponding to the original steady-state frequency, adjustment data, relative frequency offset and phase migration time; Specifically, the steady-state frequencies with the numbers 0, 1 and 2 are selected as a group, or the steady-state frequencies with the numbers 1, 2 and 3 are selected as a group; Wherein: The steady-state frequency with the number 0 is fc-△f, the steady-state frequency with the number 1 is fc-△f / 3, the steady-state frequency with the number 2 is fc+△f / 3, and the steady-state frequency with the number 3 is fc+△f; When the steady-state frequencies with the numbers 0, 1 and 2 are selected as a group, the intermediate frequency H is fc-△f / 3, and then the carrier nominal frequency is adjusted upward by △f / 3 according to the intermediate frequency, obtaining the adjustment frequency of the number 0 fc-2*△f / 3, the adjustment frequency of the number 1 0, the adjustment frequency of the number 2 fc+2*△f / 3, and the adjustment frequency of the number 3 fc+4*△f / 3; When the steady-state frequencies with the numbers 1, 2 and 3 are selected as a group, the intermediate frequency H is fc+△f / 3, and then the carrier nominal frequency is adjusted downward by △f / 3 according to the intermediate frequency, obtaining the adjustment frequency of the number 0 fc-4*△f / 3, the adjustment frequency of the number 1 fc-2*△f / 3, the adjustment frequency of the number 2 0, and the adjustment frequency of the number 3 fc+2*△f / 3; Step S2: Process the 406 satellite indication message framing signal, and convert it into modulation data according to the adjustment information; Step S3: According to the adjustment information, the carrier frequency is corrected to obtain the modulation frequency; Step S4: Use the modulation frequency to send the modulation data, and the modulation frequency corresponds to the modulation data at the same time.

2. The 406 satellite beacon phase modulation method of claim 1, wherein, Step S2 specifically comprises: Step S2.1: Obtain the 406 satellite indication message framing signal of the binary code stream; Step S2.2: Perform BPSK encoding on the 406 satellite indication message framing signal of the binary code stream to form n bit encoding data; Step S2.3: Initialize the n bit encoding data; Step S2.4: Expand the n bit encoding data into a data group, and 1 bit encoding data corresponds to xB data; Step S2.5: Modulate each bit encoding data according to the adjustment information to obtain the modulation data.

3. The 406 satellite beacon phase modulation method of claim 2, wherein, The step S2.5 specifically comprises: Step S2.5.1: Judge the first bit encoding data, If it is 1, the first xB data is corrected according to the adjustment information, so that its phase is adjusted from 0 rad to +1.1 rad; If it is 0, the first xB data is corrected according to the adjustment information, so that its phase is adjusted from 0 rad to -1.1 rad; Step S2.5.2: Judge the i-th bit encoding data, i=2,…n; If the (i-1)th bit encoded data is same as the ith bit encoded data, the corresponding xB data is maintained unchanged; If the (i-1)th bit encoded data is 0 and the ith bit encoded data is 1, the corresponding xB data is modified according to the adjustment information, so that the phase is adjusted from -1.1 rad to +1.1 rad; If the (i-1)th bit encoded data is 1 and the ith bit encoded data is 0, the corresponding xB data is modified according to the adjustment information, so that the phase is adjusted from +1.1 rad to -1.1 rad; Repeat step S2.5.2 until all encoded data is modulated to obtain corresponding modulated data.

4. The 406 satellite beacon phase modulation method of claim 1, wherein, The intermediate frequency H is obtained by the following formula: where: h j is the jth steady-state frequency.

5. The 406 satellite beacon phase modulation method of claim 1, wherein, The 406 satellite indication message framing signal includes a long frame signal or a short frame signal. 6.406 A satellite beacon phase modulation apparatus characterized by, Comprise: A reference crystal oscillator, which provides a reference frequency for the MUC; An MCU, which controls the radio frequency transceiver chip; The radio frequency transceiver chip is electrically connected with the MUC, and is used to execute the 406 satellite indication phase modulation method according to any one of claims 1-5.

7. A 406 satellite beacon phase modulation apparatus as claimed in claim 6, characterised in that, The PLL circuit inside the MCU can synthesize clock information for the radio frequency transceiver chip.

8. A 406 satellite beacon phase modulation apparatus as claimed in claim 6, characterised in that, Further comprise: A power amplifier chip, which is electrically connected with the radio frequency transceiver chip, and is used to realize signal amplification.

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